Conventionally, there has been known a turbo receiver for a single user as shown in Non-patent document 1. FIG. 13 is a diagram showing a schematic configuration of a transmitter and a receiver disclosed in Patent document 1. In a transmitter 1300, an information sequence is coded in an coder 1301 and a coding output thereof is interleaved (rearranged) in an interleaver 1302. After that, a carrier wave signal is modulated in a modulator 1303 and the modulated output is transmitted. This transmission signal is received by a receiver 1310 through a transmission path (each channel of a multipath). In the receiver 1310, a soft-input soft-output equalizer 1311 performs the equalization of a delay wave. The input of this equalizer 1311 is input into the equalizer 1311 as a digital signal of the received signal typically after the received signal has been converted into a base band and the baseband received signal has been converted into a digital signal by sampling at a frequency not less than one time the symbol signal frequency for the information sequence of the transmission signal.
The equalizer 1311 is a linear equalizer and a log-likelihood ratio Λ1(LLR), which is a probability ratio of +1 and −1 at each coding bit {b(i)}, is derived as an equalization output. Here, λ1[b(k)] is external information to be transmitted to a succeeding channel decoder 1314, and λ2[b(k)] is preliminary information provided to the equalizer 1311. The preliminary information λ2[b(k)] is subtracted from the LLR in a subtractor 1312 and the subtracted LLR is supplied to the channel decoder 1314 further via a de-interleaver 1313. This channel decoder 1314 calculates a log-likelihood ratio Λ2. Here, λ2[b(i)] is external information to be provided to the equalizer 1311 for repetition as λ2[b(k)], and λ1[b(k)] is provided to the channel decoder 1314 as preliminary information λ1[b(i)]. λ1[b(i)] is subtracted from λ2[b (i)] in a subtractor 1315 and the subtracted Λ2[b(i)] is supplied to the equalizer 1311 and the subtractor 1312 via an interleaver 1316. In this manner, the equalization and the decoding are performed repeatedly, thereby achieving the improvement of an error rate.
Further, conventionally there has been known receiving antenna diversity. FIG. 14 is a diagram showing a schematic configuration of a receiver disclosed in Patent document 2. This receiver is configured so as to obtain a receiving antenna diversity effect by combining diversity and adaptive equalization and by carrying out antenna synthesis for filter outputs at respective receiving antennas when performing single carrier transmission. As shown in FIG. 14, this receiver includes correlators 1401 and 1402 each estimating an impulse response by correlation calculation of a received signal and a reference signal, and adaptive filters 1403 and 1404 each performing matched filtering based on a weight coefficient of complex conjugate time reversal in the impulse response. This receiver further includes a synthesis circuit 1405 combining filter outputs, a delayed decision feedback sequence estimator 1406 outputting temporary decision data based on an output of the synthesis circuit 1405, a replica generator 1407 generating a received signal replica based on the temporary decision data, a preamble generation circuit 1408 generating a known signal, and switchers 1409 and 1410 supplying the received signal replica or the known signal to the correlators 1401 and 1402, respectively, as the reference signal. Moreover, this receiver includes a receiving units 1411 and 1412 and delay circuits 1413 and 1414.
Prior Art Document
Patent Document
Patent document 1: Japanese Patent Application Laid-Open Publication No. 2004-166218
Patent document 2: Japanese Patent Application Laid-Open Publication No. 2001-308763
Non-patent Document
Non-patent document 1: Tadashi Matsumoto and Shinsuke Ibi “Turbo Equalization Fundamentals and Information Theoretic Considerations”, IEICE Trans. B, Vol. J90-B, No. 1, pp. 1-16, 2007